Single umbilical artery (SUA) is one of the most common prenatal diagnoses in cases of foetal abnormality. This prospective study evaluated 77 foetuses with isolated SUAs and 77 healthy foetuses, both at 22-39 gestational weeks. We categorised gestational age into the second and third trimesters, measured the umbilical arterial blood flow parameters and calculated the umbilical vein (UV) area, umbilical artery (UA) area and UV area/UA area ratio. In the second and third trimesters, a higher UA area was obtained in the isolated SUA group than in the control group (p < .01). Furthermore, the isolated SUA group had a lower UV area/UA area ratio than the control group (p < .01), and a positive linear correlation was found between gestational age and UV area in both groups (p < .01). The presence of isolated SUAs was associated with low birth weight and a high prevalence of small for gestational age.IMPACT STATEMENTWhat is already known on this subject? Single umbilical artery (SUA) is one of the most common prenatally diagnosed foetal abnormalities and approximately 80% foetuses with SUA have isolated SUA, which is a soft indicator of chromosome abnormalities, congenital malformations and premature birth. Umbilical cord cross-sectional area can be evaluated prenatally by ultrasound imaging. Normal values increase with gestational age and foetal size in single pregnancies. Changes in umbilical cord thickness have been associated with complications during pregnancy.What do the results of this study add? The correlation between gestational age and umbilical vein area in the isolated single umbilical artery (SUA) group and control group was better than that between gestational age and umbilical artery area. UA area increased significantly in both groups before 28 weeks but not after 28 weeks, particularly in the isolated SUA group.What are the implications of these findings for clinical practice and/or further research? The study provides a reliable basis for maternal foetal monitoring during pregnancy in the isolated SUA and control groups. Objective assessment of the occurrence and development of foetuses with isolated single umbilical artery was performed.
Keywords: Foetus; haemodynamics; isolated single umbilical arteries; umbilical artery; umbilical vein.